This invention relates to pneumatic tire rims, and particularly to light commercial and truck tire rims.
Most passenger car tires today are of the tubeless type. This is not true or light commercial and truck tires. A majority of light commercial and truck tires are of the tube type.
It would be difficult to mount a tire of the tube type on a one-piece rim because it would be difficult to get the tire with its inner tube and protective flap over the outer flange of a one-piece rim. Because of this difficulty, rims for tube type tires are multi-piece, being either two-piece or three-piece.
The two-piece rim has a rim base and a detachable split flange which is frequently referred to as a lock ring. The rim base is annular, comprising a relatively wide flat annular surface having at the inner edge thereof an integral raised flange. At the outer edge of the rim is a gutter having an inner edge defined by a relatively small jog or step down from the larger diameter annular surface of the main annular surface of the rim base. At the outer edge of the gutter is a low flange or lip.
The split flange or split lock ring in the two-piece rim is an annular member which is interrupted or slit in the transverse direction. The lower or inner-diameter surface of the split lock ring has a contour which is shaped to mate with the contour of the surface of the gutter and outer lip of the rim so that the split lock ring may be placed over the lip of the gutter and locked into place against the lip.
When a tube type tire is to be mounted on the two-piece rim, as by a maintenance or repair man in a tire repair or recapping shop, the rim base is placed on the floor with the inner flange of the rim resting on the floor, i.e., with the center axis of the annular rim vertical. The tire containing an inner tube and flap are then dropped over the annular rim base. The inner sidewall and bead of the tire now rest against the inner flange of the rim base. The outer sidewall and bead of the tire have also passed over the outer lip of the rim base and are inside the lip of the rim base. The second piece of the two-piece rim, i.e., the split flange or split ring, is now placed against the outer sidewall of the tire just above the outer bead, and the split ring is pushed or knocked downwardly (inwardly relative to the tire when mounted on the wheel), as by a hammer or other appropriate tool, until the split lock ring snaps into place. In this position, upon inflation of the tire, the split lock ring becomes, or should become, "locked" and able to withstand the outward forces to which it will be subjected by the high air pressure (85-90 lbs) in the tire when cold, and to the substantially higher tire pressures and outward forces to which the tire will be subjected when the tire is in use under hot road conditions.
The three-piece rim has a rim base (generally similar to that of a two-piece rim), an integral (non-split) annular side ring, and a split lock ring. The split lock ring has an outer lip. It interfits between the rim base and the annular side ring. The split lock ring is contoured on its inside-diameter surface to mate with the gutter and outer lip of the rim base. The other side of the split lock ring is contoured to mate with the annular non-split side ring.
To mount the truck tire, as in a repair or recapping shop, the first piece of the three-piece rim, i.e., the rim base is placed on the floor with its inner flange resting on the floor and the center axis of the annular rim vertical. The tire, containing inner tube and flap, is then dropped over the annulus of the rim base, and the tire takes a position similar to that described above with respect to the two-piece rim. The non-split annular side ring is next placed over the outer lip of the rim base gutter and against the outer sidewall of the tire. Lastly, the split lock ring is inserted over the lip of the gutter and positioned between the inside diameter of the non-split annular side ring and the gutter and lip of the rim base. When the truck tire is inflated, the inside diameter surface of the split lock ring mates, or should mate, with the gutter and outer lip of the rim base while the outside surface and lip of the split lock ring mates, or should mate, with the non-split annular side ring.
Tires are usually repaired or recapped in a shop or other building in which more than one repairman or worker is working and more than one tire is being repaired or recapped. As a consequence, the various parts of different multi-piece rims may be scatterred around the floor and it may easily happen that a split ring of a particular make or type of two-piece rim may be picked up by a worker and assembled with a rim base which is not its mate. Or, the split ring of a three-piece rim may be picked up and assembled with a rim base and/or a side ring which are not its intended mates.
Multi-piece rims are made by several different manufacturers, and while the rim pieces of different manufacturers may appear to be generally similar in size and shape as compared to those of other manufacturers, the parts in fact are not identical, and the differences therebetween, although appearing to be small, may be enough to prevent a lock ring of one manufacturer from mating "lockingly" with the rim base of another manufacturer, or of another type of the same manufacturer. In such cases, when the tire is inflated to a pressure, for example, of 90 lbs., the split lock ring may fly out with explosive force. Serious injury has occurred to repairmen or other workers as a result of such explosive separation of rim parts caused by incorrect matching of parts of multi-piece rims.
An explosive separation of parts of multi-piece rims may also occur on the streets or highway when a lockring dislodges due to incorrect matching of parts. In such cases, the split ring and/or side ring may fly across the highway and smash into a passing vehicle or pedestrian with very serious consequences.